My mom always stressed the importance of wearing fresh undies each day just in case I got into an accident and had to be taken to the hospital. God forbid the ER docs would notice the underwear I was wearing weren’t sparkly clean, was her thinking. I know I’m not the only one who got that advice.

Underwear, no matter what our mother’s may have said, turn out to be a leading economic indicator. Well, maybe not leading and maybe not for females. But, when it comes to the guys, how many pairs of briefs and boxers they’re purchasing apparently says a lot about current economic conditions. There’s even an index for it—the Men’s Underwear Index, MUI. Honest.

According to a WashingtonPost.com story today, when guys aren’t buying skivvies as often as normal it’s a sign that the economy is in the crapper. Really.

The theory for this is based upon the notion that men’s underwear is considered a stable because it’s a necessity. So when money is tight, men apparently keep wearing their old underwear longer than they do in times when money is freer.

Mintel, the name of the research company that’s uncovered this data, has been looking into men’s underwear since 2003. They noticed that sales of men’s knickers started to decline last year as the recession took hold and are expecting that trend to continue.

Then again, spokespeople from both Sears and Target say sales in their respective underwear departments have been looking up. Go figure.

So how many pairs of men’s underwear do guys buy? Mintel’s research points out that men buy an average of 3.4 pairs a year. (I saw a guy once who was wearing that .4 of a pair. It wasn’t pretty.)

Depending upon how the figuring is done, though, while sales of four-packs or more have fallen from 68 to 66 percent in the last four years, buyers of single-packs have been on the rise—up 3 percent over that same time frame.